<HTML><HEAD><TITLE>div(+Number1, +Number2, -Result)</TITLE>
</HEAD><BODY>[ <A HREF="index.html">Arithmetic</A> | <A HREF="../../index.html">Reference Manual</A> | <A HREF="../../fullindex.html">Alphabetic Index</A> ]
<H1>div(+Number1, +Number2, -Result)</H1>
Evaluates the integer quotient Number1 div Number2 and unifies the resulting
value with Result.


<DL>
<DT><EM>Number1</EM></DT>
<DD>Integer.
</DD>
<DT><EM>Number2</EM></DT>
<DD>Integer.
</DD>
<DT><EM>Result</EM></DT>
<DD>A variable or integer.
</DD>
</DL>
<H2>Description</H2>
   This predicate is used by the ECLiPSe compiler to expand evaluable
   arithmetic expressions.  So the call to div(Number1, Number2, Result) is
   equivalent to
<PRE>
    Result is Number1 div Number2
</PRE>
    which should be preferred for portability.
<P>
    This division operates on integer arguments, and delivers an
    integer result rounded down towards negative infinity (floored). 
    The corresponding remainder is computed by the mod operation, such
    that the following equivalence always holds:
<PRE>
    X =:= (X mod Y) + (X div Y) * Y.
</PRE>
    The relationship with floating-point division is:
<PRE>
    X div Y =:= integer(floor(X/Y)).
</PRE>
<P>
   In coroutining mode, if Number1 or Number2 are uninstantiated, the call
   to (div)/3 is delayed until these variables are instantiated.

<P>

<H3>Modes and Determinism</H3><UL>
<LI>div(+, +, -) is det
</UL>
<H3>Exceptions</H3>
<DL>
<DT><EM>(4) instantiation fault </EM>
<DD>Number1 or Number2 is not instantiated (non-coroutining mode    only).
<DT><EM>(5) type error </EM>
<DD>Number1 or Number2 is a number but not an integer.
<DT><EM>(24) number expected </EM>
<DD>Number1 or Number2 is not of a numeric type.
<DT><EM>(20) arithmetic exception </EM>
<DD>Illegal arithmetic operation:  division by 0
</DL>
<H2>Examples</H2>
<PRE>
Success:
      X is 10 div 3.		( gives X = 3)

      div( 10,  3,  3).
      div(-10,  3, -4).
      div( 10, -3, -4).
      div(-10, -3,  3).
Fail:
      div(1, 2, 3).
      div(6, 2, 3.0).
      div(5, 2, r).
Error:
      div(A, 2, 6).              (Error 4).
      div(6, 2.0, 3.0).          (Error 5).
      div(2, 0, Result).        (Error 20).
      div(4 + 2, 2, 12).        (Error 24).
</PRE>
<H2>See Also</H2>
<A HREF="../../kernel/arithmetic/is-2.html">is / 2</A>, <A HREF="../../kernel/arithmetic/FF-3.html">// / 3</A>, <A HREF="../../kernel/arithmetic/mod-3.html">mod / 3</A>
</BODY></HTML>
